Copper-magnesium alloys of improved properties



Patented May 9, 1939 PATENT OFFICE IIVIPROVED PROPERTIES Franz R. Henseland Earl I. Larsemlndianapolis,

Ind., assignors to P. R. Mallory & Co. Inc., Indianapolis, Ind., acorporation of Delaware No Drawing, Application August 12, 1938, SerialNo. 224,496

3 Claims.

This invention relates to alloys and more particularly to copper alloysof improved characteristics. I

The object of the invention is to produce an 5 improved copper basealloy.

Another object is to produce an age-hardened copper-magnesium alloy.

Another object is to produce a copper alloy which has an excellentcombination of hardness,

electrical conductivity and resistance to annealing? Other object of theinvention will be apparent from the following description taken inconnection with the appended claims.

The present invention comprises a combination of elements, methods ofmanufacture and the product thereof, brought out and exemplified in thedisclosure hereinafter set forth, the scope of the invention beingindicated in the appended claims.

The invention relates to the alloys of coppermagnesium and a metal takenfrom the iron group, characterized by the addition of silicon adapted toform silicides with anelement taken from the iron group. While thesealloys may vary in their physical characteristics with the type oftreatment received and the proportion of various ingredients, they willgenerally be characterized by high conductivity and hardness ,and

by heat and oxidation resistance.

According to the preferred method of carrying out our present invention,an alloy is made containing copper, magnesium, an element from the irongroup and silicon in approximately the following proportions:

Per cent Magnesium 0.1 to 3 Material from the group: nickel, cobalt,

iron 0.1'to 5 40 Silicon 0.1 to 3 Copper Balance.

It is possible likewise to improve the alloys consisting primarily ofthe composition described above, but also containing small percentagesof additional ingredients, such as silver, zinc, cadmium, tin,zirconium, calcium, lithium, titanium and manganese. In some instancesphosphorus, aluminum or beryllium may be substituted, in

' Whole or in part, for the silicon since they also form intermetalliccompounds with the iron group metals.

In carrying out'the present invention, a copper-magnesium alloy mayfirst be made, according to the conventional alloy making procedure ofthe prior art, and then the hardening elements consisting of a metaltaken from the iron group, in combination with the compound formingelement silicon, may be added. It is also possible, however, to producefirst a copper alloy containing an element taken from the iron group. 5The metal from theiron group may be added as such, or in the form of ahardener alloy or in the form of a compressed briquette, consisting ofvarious proportions of copper powder and powder of the element takenfrom the iron group. 10 After the melt, consisting of the aboveingredients, reaches a certain temperature, the-magnesium may be added,preferably in the form of a hardener alloy. The silicon may be added,either before the addition of the magnesium or 5 afterwards. 7

After the alloy has. been prepared according to such alloying methods asdescribed above, the heat treatment may be carried out as follows: Thealloy in the form of a billet or a sand 20 casting or any form, israised in temperature to above 700 degrees C., and preferably to atemperature in the order of 800 to 1000 degrees C. The alloy is thenquenched from this high temperature and subsequently aged at a tempera-25 ture below 700' degrees C., and preferably in the range between 300and 600 degrees C. This heat treatment results in considerableimprovement in the hardness of the alloy. For example, an

alloy containing 30 Per cent Magnesium 0.5 Nickel 2.25 Silicon 0.5Copper Balance. 35

will have a Rockwell B hardness in the quenched condition, of 10 to 25.After aging for 16 hours at 450 degrees C., this hardness can be raisedto Rockwell B.

An alloy of Per cent Magnesium 0.55 Nickel 2.14 Silicon 0.22 CopperBalance. 45

iron group in combination with silicon, adapted to form silicides withsuch metals of the iron group.

For example, an alloy of Per cent Magnesi 0.70 Cobalt 2-.11 Silicon 0.21

Copper Balance.

. This hardness is higher than that obtained by cold working thismaterial after aging. The best results are obtained if the cold workingis quite severe such as 50 to 60%.

Our experiments have shown that if alloys are being made which'do notcontain magnesium, very heterogeneous products are obtained. This isparticularly true if the materials are used for pouring into sand moldsand are afterwardsv heat treated without any further hot or coldworking. A great number of test pieces have been made and tensile testresults varied from 2,000 p. s. i., to over 60,000 p. s. i. No apparentreason could be found for such great differences. Apparently, themelting conditions and the pouring temperature must afiect the materialsadversely, if they do not contain magnesium. The molten metals absorbgases which are given up during solidification and which are containedwithin the grain boundaries of such materials. In heat treating, thesegases or other impurities expand and either fracture the grainboundaries completely or weaken same considerably.

The addition of magnesium to copper has completely eliminated suchdeleterious eflects, the magnesium acting in various ways. It firstcompletely deoxidizes the melt, it acts as a strong grain refiningelement and it makes materials more stable during subsequent heattreatments. It also produces a layer of oxide if heated in air, whichprotects the metal from further oxidation and in this respect alloyscontaining approximately 1% magnesium are found to be as good asaluminum bronzes containing. as much as 5 to 10% aluminum. While ittherefore was impossible to produce a satisfactory and commercialproduct with copper alloys of the type described, but free of magnesium,the present invention has overcome all of these inconsistencies and hasresulted in the development of a metal which can be reproduced withinclose limits of tolerances as far as the physical properties areconcerned.

The sand cast alloys containing substantial percentages of magnesium,such as 0.25% to 2%, were all found to have a high tensile strengthexceeding 65,000 p. s. 1. Furthermore, these alloys show a considerableamount of elongation and a reduction in area. Such ductility in castalloys is a factor which contributes greatly to safety in operation,because a material which shows a high reduction in area will yieldlocally, and not fracture if excessive stresses are applied.

It was further found that these new improved alloys have electricalconductivities exceeding 35% of that of pure copper. The new alloys,therefore, will make ideal sand casting materials which may be used fora large variety of applications such as structural parts in electricalmachinery, or parts which have to withstand heat and oxidation. Alloysof this type were found to be very satisfactory for large castings,particularly large wheels such as are used for feeding rolls, inelectric welding of pipe. The alloys are also proposed for electriccontacting elements of the type comprising pressure exerting weldingelectrodes and the like.

It also has been found that materials free of magnesium, have a tendencyto fire crack at temperatures in the approximate range of 350 to 800degrees C. Materials which have been previously hardened and arere-heated to such a range, have a decided tendency to form cracks. Withour new material, this tendency has been very much decreased, because weprovided a material of higher and more uniform strength of a veryhomogeneous and fine grained texture.

While the present invention as to its objects and advantages has beendescribed herein as carried out in specific embodiments thereof, it isnot desired to be limited thereby but is intended to cover the inventionbroadly, and within the spirit and scope of the appended claims.

What is claimed is:

1. An alloy composed of 0.1 to 3% magnesium, 0.1 to 5% of a materialselected from the group consisting of nickel, cobalt and iron, 0.1 to 3%silicon, and the balance copper.

2. An age-hardened alloy composed of 0.1to 3% magnesium, 0.1 to 5% of amaterial selected from the group consisting of nickel, cobalt and iron,0.1 to 3% silicon and the balance copper characterized by high hardnessand tensile strength, said alloy having the property of resisting theeffects of heat at elevated temperatures for extended periods of time.

3. An electrical contacting element formed of an alloy composed of 0.1to 3% magnesium, 0.1 to 5% of a material selected from the groupconsisting of nickel, cobalt and iron, 0.1 to 3% sili-. con, and'thebalance copper.

FRANZ R. HENSEL. EARL I. LARSEN.

